|Sycamore and Maple (Acer)
As wide as long (7 to 15 cm) usually glabrous (hairless) except for some hairs in the
axils of the main veins. The leaves are palmate, being divided into 5 lobes. The base is
cordate (heart-shaped) and the margins are coarsely serrate 'jagged'). Flower stalks
and young twigs are also hairless. Presumable, the large lobed plane-like leaves gave
rise to the name 'pseudoplatanus'.
Hermaphrodite and male flowers, yellow-green, borne on pendent catkins (each 7.5 to
20 cm long) of 50 or more (60 to 100) flowers, with the youngest flowers at the tip.
Floral formula, Acer genus: K 5 C 5 A 5,8,10 G(2/). The ovary is superior. Each catkin
is a pendulous raceme - each flower is borne on a short stalk. The proportion of male
flowers varies, but is usually less than 60%, though some trees are almost entirely
male. The flowers on the tip of the catkin are male. The male flowers open first in
April/may. Younger trees have more male flowers. The hermaphrodite flowers are
scented and produce nectar, attracting bees and some flies as presumed pollinators.
Above: a sycamore (sycamore maple, Acer pseudoplatanus) in Fredville Park, Kent, England.
('Sycamore' is also applied to certain plane trees and a species of fig, which are not related to
the sycamore maple). The sycamore is a species of maple native to central Europe.
The sycamore is deciduous, new buds opening first in early spring (March). The sycamore is a
large tree, reaching 20 to 35 metres in height (60 to 105 feet) though most mature trees are
between 18 and 24 m. It is very fast growing on limestone, producing annual shoots of up to 1
metre in length until the tree is 5-6 metres in height. Growth in height and diameter is fastest in
the first 40 years, and is noticeably levelling off by 100+ years. The trunk may attain a diameter
of 1.8 m, rarely 2.7 m (at 1 m above ground level). The maximum lifespan is 400 to 600 years.
The seedlings are very shade tolerant, but mature trees are not and tend to be overcrowded
and killed by rivals and so very old trees are rarely found in woodland.
A native to continental Europe and parts of Asia, also widely planted in Britain from the 15th
century, the sycamore prefers mountainous habitats, growing as a sizeable tree up to 1510 m in
the Bavarian Alps, and up to 1650 m as scrub. In Britain it is found in lowlands and up to 460 m.
It is more tolerant to wind and salt spray than most large deciduous trees. It is quite frost tolerant.
The sycamore prefers moist, deep, basic, freely-draining soils and cool conditions, but does not
tolerate water-logging. Moist loamy mountain slopes are ideal.
The samara of Norway maple (Acer platanoides).
In the field maple (Acer campestre) the wings are
held out more straightly at about 150 degrees,
whilst in sycamore the wings are at 90 degrees or
even bent parallel to one-another. In field maple,
Acer campestre, the wings are typically almost
180 degrees apart, whilst in Montpelier Maple
(Acer monspessulanum) they are almost parallel
to one-another (at zero degrees) and in Italian
maple, Acer opalus, they are at an angle of about
The tap root is small and the root system is compact but deep. The roots develop
large, dense root hairs. Endotrophic mycorrhiza form.
The bark of the sycamore is smooth and greyish when young (greenish in some trees) but
flakes off in definite brownish scales when older, sometimes leaving pinkish patches beneath.
The lenticels are small, up to 0.5 mm, and round or slightly elongated.
Above: the bracket fungus Polyporus squamosus, prefers sycamore, elm
and beech. Here it is growing on the sycamore pictured above.
Germination and Growth
Some seeds overwinter, others, especially those formed early, germinate rapidly.
Germination is of the epigeal type, meaning that the two cotyledons emerge above
ground, cast off the seed coat and photosynthesise as a first pair of proto-leaves. About
10-30% of the seeds, especially those produced at the tip of the raceme, are empty.
The seedlings (but not the mature trees) are very shade-tolerant and very fast growing.
The trunk forks very rapidly as the tree grows, producing a very extensive spreading
Uncommon. Suckers only form on poor light soils.
Sycamore exhibits monopodial growth.
Jones, E.W. 1945. Acer Pseudo-Platanus L. Journal of Ecology: pp.220-237
To be continued ...
Article last updated: 12/5/2014
Above: a catkin of Acer pseudoplatanus with some conspicuously ripe male flowers with
protruding anthers. The remaining flowers are often described as female, but appear
to have unripe stamens and so are probably hermaphroditic. In a recent study in
German trees, most Acer pseudoplatanoides were found to be protandrous (the male
organs ripen first followed later by the female organs, so the trees change functional
sex) whilst many were protogynous (female organs ripening before the male organs)
and a few were entirely male. (Tal, O. and W. Morawetz. Reproductive biology of the
main tree species at the canopy crane investigation site. Clearly, the gender of whole
trees as well as individual catkins is complicated in the sycamore maple!
The fruit of maples is essentially a winged nut, called a samara (or 'key'). The two
wings of this familiar and distinctive fruit cause it to rotate when falling through the air,
generating lift as an aerofoil and carrying it over greater distances for dispersal. On
camera film these fruit, and winged fruit of other trees such as elm, produce motion
streaks (or double images when raster scanned into fields and frames) which have
caused quite a stir, accounting for many of the mysterious 'rods' that people have
seen and thought to be beings from another dimension! The fruit usually travel less
than 100 m from the parent tree, but some have been recorded drifting for up to 4 km.
Above: flowers of Acer platanoides (Norway Maple), left, compared with those of Acer
pseudoplatanus (sycamore maple), right.